Without limiting the scope of the present inventions, their background is described with reference to setting tools, downhole force generators and downhole power units and improvements thereto. It is typical in hydrocarbon wells to “set” or actuate downhole tools, such as packers, bridge plugs, high-expansion gauge hangers, straddles, wellhead plugs, cement retainers, through-tubing plugs, etc. Additionally, some of these tools are later “unset” for retrieval. Setting tools are run-in, and in some cases retrieved, using various conveyance methods such as a wireline, slickline, or coiled tubing. The generic name for the running tool which provides the large setting forces required is a setting tool. Several types of setting tool and downhole force generators (DFG) are known in the art, including those operated mechanically, electrically, chemically, explosively, hydraulically, electro-mechanically, etc.
One type of DFG uses electro-mechanical power, where the DFG converts electrical power, typically provided by a battery unit, into mechanical movement, typically rotary or longitudinal movement of a shaft or power rod. One such setting tool is the DPU (trade name) Downhole Power Unit available from Halliburton Energy Services, Inc. Halliburton's DPU provides an even stroke with a force profile that gradually builds over time. However, the DPU requires a large stack of batteries to drive the motor. The power output needed from the batteries limits the maximum operating temperature for the batteries and for the tool. The use of relatively large quantities of lithium batteries, for higher temperature operations, limits the ability to easily transport the DPU and is a significant cost driver.
Additionally, some industry pyrotechnic setting tools, such as the Baker 20 Setting Tool, available from Baker Oil Tools, Inc., utilize a pyrotechnic material to generated pressure. A chamber containing a high pressure gas houses a floating hydraulic piston with an oil filled chamber below. The hydraulic oil is pressured by the expanding gas, providing hydraulic power which performs the setting task. Disadvantages to such pyrotechnic setting tools include compliance with extensive and costly regulations, including special shipping and handling by trained personnel, storage on licensed premises, third party notification when shipping, inspections by official personnel, and routine inspections. Further, The Baker 20 setting tool delivers peak force at the beginning of the stroke with diminishing force afterwards, especially as the gas generated by the pyrotechnic reaction cools.
Hydrostatic setting tools convert ambient hydrostatic pressure in a wellbore into hydraulic force to set the downhole tool. But many prior art hydraulic setting tools suffer from a very quick force-time profile, where the hydrostatic pressure is applied very quickly. The components in the setting tool then move in response at rapid speeds, which can damage sealing elements and break metallic components.
Further disclosure relating to downhole force generators, their operation and construction, can be found in the following, which are each incorporated herein for all purposes: U.S. Pat. No. 7,051,810 to Clemens, filed Sep. 15, 2003; U.S. Pat. No. 7,367,397 to Clemens, filed Jan. 5, 2006; U.S. Pat. No. 7,467,661 to Gordon, filed Jun. 1, 2006; U.S. Pat. No. 7,000,705 to Baker, filed Sep. 3, 2003; U.S. Pat. No. 7,891,432 to Assal, filed Feb. 26, 2008; U.S. Patent Application Publication No. 2011/0168403 to Patel, filed Jan. 7, 2011; U.S. Patent Application Publication Nos. 2011/0073328 to Clemens, filed Sep. 23, 2010; 2011/0073329 to Clemens, filed Sep. 23, 2010; 2011/0073310 to Clemens, filed Sep. 23, 2010; and International Application No. PCT/US2012/51545, to Halliburton Energy Services, Inc., filed Aug. 20, 2012.
It is an object of the invention then, to provide a downhole force generator or setting tool with a relatively low cost. It is a further object of the invention to provide a DFG capable of operation in high temperature environments. It is a further object of the invention to provide a DFG which delivers high force over a long stroke. It is a further object of the invention to provide a DFG having a customizable force-time profile. It is a further object of this invention to provide a setting tool which is not subject to the regulations and restrictions of typical pyrotechnic setting tools. Other objects and benefits will be apparent to those of skill in the art.